One of the current development trends of vehicle lighting is the effort to distinguish a particular car model or model series from competitors' products. To produce interesting optical and designer effects, light guides are used to a great extent that are an integral part of the front or rear lamp of the vehicles, and their light-emitting surfaces are one of the predominant elements of the appearance of the car. In light guides whose transversal profile has a circular or mushroom-like shape, the source of light in the form of LED is usually positioned on one or both of the outwardly oriented frontal surfaces of the light guide. The light guide is generally attached to a part of the light device, e.g. to the covering mask, by means of fixing elements that are part of the light guide. Fixing of the light guide to the other components of the light device must meet requirements not only from the functionality point of view, but it must also meet the designer and functional requirements for the light characteristic of the output light trace.
A light device consisting of a light guide having a longitudinal shape at the front of which a light source is arranged and whose case transmits light in a certain part, forming the output surface for the exit of light rays, is known from the document EP1775511. A reflective surface of the case that is fitted with optical elements (prisms) is arranged opposite the output surface. One part of the rays flowing through the light guide reflects from the reflective side (from the optical elements) to the direction towards the output side of the light guide and exits through the output side of the light guide. The other part of the rays passes through the reflective side out of the light guide, hits a diffusion part arranged outside the light guide and reflects back, passes through the reflective side, reenters the light guide and then exits the light guide through the output side. The light device according to the document EP1775511 is disadvantageous mainly because between the diffusion layer and the light guide there is a free space, which reduces efficiency of the optical system.
A number of designs of fixing of the light guide are known in the prior art. E.g., the document CZ20100955 discloses a light guide for the light equipment of motor vehicles that is supplied by light emitting diodes (LED), which consists of a transparent material and is fitted with a fixing part. The fixing part of this light guide is a longitudinal fixing fin that is installed along more than one half of the light guide length. A disadvantage of this design is the fact that the front light emitting surface of the light guide acts as a cylindrical lens that magnifies every item that is found behind it. The fixing elements of the light guide, e.g. clips, are always visible and at the same time impair the output characteristics of the output light trace, e.g. intensity and homogeneity of the emitted light beam. The fixing elements of the light guide complicate the transmission of light from the light source, reducing the efficiency of both binding the light into the light guide and efficient guiding of light in the light guide. At the fixing elements of the light guide, the light gets unbound and reduces its optical efficiency. Another disadvantage is the fact that for the production of the fixing elements that represent an integral part of the light guide, slider mechanisms in the injection mold are necessary.
The document U.S. Pat. No. 9,182,095 describes a design of a signaling lamp containing a flat shaped carrier, whose shape in its bottom part corresponds to the shape of the light guide in the transversal direction. In its top part, the carrier is fitted with a fixing zone in the form of fixing elements arranged in the form of a continuous row of fixing arms that are fitted with fixing hooks at their free end. To fit the light guide in the pre-determined position, the light guide is equipped with longitudinally arranged ribs cooperating with the fixing hooks. Opposite the fixing ribs, the fixing element is fitted with the bottom support surface of the light guide. The fixing element is further equipped with a lateral contact surface designed to support the light guide at its rear, not light-emitting, surface. The lamp comprises a covering mask that is situated in front of the light guide, as seen from the front, and is designed to mask the fixing zone of the light guide and other uninteresting parts of the lamp from the designer point of view, the covering mask being seated on the fixing element. A disadvantage of this solution is the fact that the light guide is not fixed in any way between the fixing elements having the form of fixing hooks, and in these areas, undesired vibrations and subsequent mechanical damage of the light guide or the fixing elements might occur. The larger number of components of this fixing system also represents a drawback, both from the point of view of financial costs and from the point of view of production complexity of individual components and their completion into the final product.
The object of the present invention is to eliminate the above mentioned disadvantages of the prior art, so that no fixing elements can be visible in the view and light-emitting part of the light guide, that the light guide can be homogeneous all along the length of its active surface in the lit as well as unlit state, and that no fixing elements should hinder the transmission of light to ensure high optical efficiency of the light guide. The entire fixing system must be robust from the mechanical point of view to avoid undesired vibrations, and at the same time the fixing system must be easy to produce with low financial costs of the production and completion of the final product.